1. Field of the Invention
The present invention relates generally to a document preparing apparatus using a computer, and more particularly to a hyper-text document preparing apparatus in which a document having a hyper-text form is prepared.
2. Description of the Related Art
The transmission and reception of information among a plurality of terminals far from each other through a computer network has been recently performed on an extensive scale. In particular, because a piece of information stored in a computer on an information supplier side has a reference relationship with another piece of information stored in the same computer or a piece of information stored in a computer on another information supplier side, an information transmitting system in which pieces of first information respectively having a reference relationship with a piece of second information are transferred from various computers having the first information to a computer having the second information has been quickly spread.
In this information transmitting system, a reference relationship among all pieces of information is expressed in a hyper-text form composed of a plurality of nodes and a plurality of links respectively connecting a pair of nodes. For example, a Hyper-Text Markup Language (HTML) which is gradually standardized in an IETF internet draft is often used to express a reference relationship among pieces of hyper-text information transmitted through a computer network. The HTML is a symbolic language based on SGML and defined in ISO (international standardization organization) 8879:1986.
The HTML is a type of page description language, and each page can be expressed by a single node or a plurality of nodes. A piece of link information for identifying both first information transmitted to second information for reference and the second information is written in an arbitrary position of a page to express each link connecting a pair of nodes by using an identifier allocated to each node. The link information indicates only a reference relationship between information, and any relationship between contents of information is not indicated by the link information.
The hyper-text is general as a data base type for the computer, and many methods and apparatuses for preparing a hyper-text type document are proposed.
2.1. Previously Proposed Art
FIG. 1 shows a conceptual information structure of a conventional hyper-text document as a first prior art.
As shown in FIG. 1, a hyper-text document is composed of a plurality of nodes respectively denoting an element of the document and a plurality of links respectively indicating a reference relationship between a pair of nodes. In the hyper-text document, a degree of freedom in the reference relationship between a pair of nodes is high, so that an information structure of the hyper-text document can be variously designed. In contrast, because the number of links is increased with the number of nodes, there is a drawback that a linking relationship among the nodes is complicated. That is, in cases where the linking relationship among the nodes is complicated in the hyper-text document, it is troublesome for a document preparing person to maintain the hyper-text document, and it is difficult for a document reading person to understand the hyper-text document and find out a particular node. Also, it is difficult to manage a plurality of nodes as a set, it is required to add a large number of links for one or more nodes relating to a particular node each time the particular node is newly added, and it is required to revise a large number of links for one or more nodes relating to a particular node each time the particular node is newly added.
In other prior arts for the hyper-text document preparing apparatus, a link management can be easily performed. For example, as a second prior art, a Published Unexamined Japanese Patent Application No. H3-192462 (1991) and a Published Unexamined Japanese Patent Application No. H4-211865(1992) are proposed. In these applications, the relationship among a plurality of documents having a plurality of predetermined formats is defined in advance, so that the necessity for spreading a link each time a document is prepared is eliminated. As a third prior art, a Published Unexamined Japanese Patent Application No. H6-243024 (1994) is proposed. In this application, a concept of nodes and links is extended to a new concept of fields and anchors, each field is composed of a plurality of nodes arranged in a set, each field has information relating to a meaning represented by a node set of field, so that a relationship in meaning between nodes is clarified.
Therefore, in the second and third prior arts, a link concept denoting the simple reference relationship between the nodes included in the hyper-text document is extended, and the difficulty in the link management is improved.
2.2. Problems to be Solved by the Invention
However, in the first prior art, because each link of the hyper-text document written according to the conventional HTML has only a function of reference from one node to another node, an interface used as a reading means is used for only reference.
Also, in the second prior art, a document to be prepared is limited to a plurality of predetermined format types of documents relating to each other such as a specification document, an account document or the like. Therefore, the first prior art is not appropriate for a hyper-text document preparing apparatus in which a plurality of types of documents having various formats are used. That is, because a format of the document is limited to one of the predetermined formats, a degree of freedom in expressing the document is lowered.
Also, in the third prior art, because an interface used by a reader depends on contents of the field, the link management for documents performed by using the same interface cannot be simplified. That is, a reader is required to understand the meaning represented by a node set of field and to use an interface corresponding to the meaning for the purpose of referring to the field for a piece of particular information relating to the meaning, so that the interface used as a reading means is limited.